] o m 1 of Natural Pr0du-i~ Vol. 52, NO.2 , pp. 41 1-414, 1Zclr-AP 1989
411
P-PHENYLETHYLAMINE-DERIVEDAMIDES FROM PIPER GUAYRANUM ANDERSON MAXWELL.and DAVERAMPERSAD
Department of Chemistry, The Universityoftbe West Indies, St. Augustine, TrinicicldandTobago, West Indies ABSTMCT.--The acetone extract of the aerial parts of Pipgwyranum yielded tembamide acetate [l]and alatamide 121 but not tembamide 131. Compound 1 has not been previously reported as a natural product while both 2 and 3 has only been encountered so far in species of Rutaceae
Pipergmyranurn C . K . (Piperaceae)is a tall, slender shrub that is found in
shady, elevated regions of Trinidad, Tobago, and Venezuela (1). There is no record of folkloric medicinal use of this plant, and there appear to be no reported chemical studies either. We wish to report the results of our studies on the aerial parts of P . guayranurn occurring in Trinidad. Repeated vacuum liquid chromatography (vlc) of the Me,CO extract resulted in the isolation of three crystalline compounds. The most polar compound 1 was obtained as white needles, mp 159" (petroleum ether/Me,CO). High resolution eims gave an [MI+ (at rnlz 3 13.1308) which indicated a molecular formula of C,,HI9NO4 (EM)+ calculated 313.1314). Four bands, at 208, 225,270, and 278 nm, were observed in the uv spectrum. The ir spectrum exhib-
ited absorptions at 3315, 1727, 1645, 1532, and 1510 cm-' indicating the presence of both amide and ester groups. 1 H nmr (Table 1)suggested a 1,4-disubstituted aromatic ring (AB type fourproton doublet of doublets at 6 6.92 and 7.35) as well as a monosubstituted one (five-proton multiplet at 6 7.45-7.83). Acetate (three-proton singlet at 6 2.12) and aromatic methoxy (three-proton singlet at 6 3.82) groups were also indicated. On complete exchange after the addition of D,O, the broad signal at 6 6.40 disappeared, and, significantly, the two-proton signal at 6 3.85, originally a triplet, became a doublet ( / = 6 Hz). This suggested that these two protons are adjacent to the nitrogen atom in compound 1 and are probably coupled to the methine proton at 6 5.97. Decoupling studies confirmed this, because irradiation of the triplet at 6 5.97 caused
OYe
OMe
O y "
1 R=Ac
3 R=H
O Y "
2
4 12
Journal of Natural Products
1
mol. 52, No. 2
3
2
~
H-1 . . . H-2 . . . H-2', 6' . H-3', 5' . H-2", 6" . H-3", 4", 5" Ac . . . . 4'-OMe . N-H . . .
....
.... . . . . ....
....
. . . .... . . . . . . . .
3.85(t,J=6) 5.97(t,] = 6) 7.35(d,]=9) 6.92(d,]=9) 7.75 (m) 7.50(m) 2.12(s) 3.83(s) 6.40(brs)
the triplet at 6 3.85 to collapse to a doublet while irradiation at 6 3.85 resulted in a singlet at 6 5.97. All the evidence clearly pointed to the structure indicated for 1. I3C n m r (Table 2) fully corroborated this structure which was also supported by eims. The latter showed important fragments at m/z {M-HOAc)+ 253.1121, IMC6H5C0",]+ 192.0805, {M C6H5CO-HOAc-OMe)+ 117.0582, and {C6H5CO]+ 105.0341.
Carbon 1. . . . . . 2 . . . . . . 1' . . . . . 2'and6' . . 3'and5' . . 4' . . . . . 1" . . . . . 2"and6" . . 3"and5".. 4" . . . . . 4'-OMe . .
....
. . . .
....
.... .... ....
....
....
. . . . .... . . . .
....... -oc=o . . . . . . -COMe
-CONH
. . . . . .
Chemical Shift 45.0 75.0 130.8 128.0b 115.3 161.0 135.5 129.7 129.2b 132.6 55.6 21.5 172.0 168.5
'Chemical shifts relative to T M S are given in 6 (pprn). Assignment of the signals was based on the]-Modulated Spin Echo ',C-nmr spectra and on calculations of chemical shifts from empirical rules. bAssignmentsmay be interchanged.
7.65(d,]= 14) 6.22(d,]= 14) 7.30 (d,J = 9) 6.85 (d,] = 9) 7.80(m) 7.50 (m)
3.70(m) 4.93 (dd,J = 3.5,7.5) 7.35 (d,] = 9) 6.93 (dJ= 9) 7.80(m) 7.47 (m)
3.81(s)
3.84(s) 6.60(brs)
-b
Mild hydrolysis of compound 1 gave the crystalline alcohol 3, mp 147-148". All the spectral data indicated its identity with the known tembamide {37, which has been prepared synthetically ( 2 4 ) and has also been also isolated from several species of Rutaceae (4-10). For example, the uv spectrum gave bands at 209, 224, 270, and 279 nm, and the ir spectrum showed diagnostic absorptions at 3440 (br) and 1655 cm-'. The 'Hn m r spectrum of 3 (Table l), while virtually identical in the aromatic region to that of 1, differed from it in three significant respects: (a) the singlet at 6 2.12 in the spectrum of 1 was absent in the spectrum of 3; (b) the signal assignable to the benzylic methine proton appeared at 6 4.93 (doublet of doublets) in the spectrum of 3, whereas it occurred at 6 5.97 (triplet) in the spectrum of 1;and (c) the signal due to the methylene protons a to nitrogen, which was a simple triplet at 6 3.85 in the spectrum of 1, appeared as a complex multiplet (6 3.354.08) in the spectrum of 3. Interestingly, after D20exchange this multiplet simplified to a double AB doublet of doublets. As expected, the eims closely resembled that of 1. Significantly, the fragment ion corresponding to loss of C6H,CONH, was found at mlz 150, replacing the fragment at m/z 192 observed in the case of 1. Compound 2 was isolated as white
Mar-Apr 19891
Maxwell and Rampersad:
needles, mp 188-189" (petroleum ether/Me,CO). It gave bands at 204, 222, and 308 in the uv spectrum and showed ir absorptions at 3320, 1645, and 945 cm-'. Consideration of these data and comparison of the 'H-nmr spectrum (Table 1) with that of 1 strongly suggested that 2 was related to 1 via loss of HOAc. Thus, the methyl singlet at 6 2.12 and the triplets at 6 3.85 and 5.97 in thespectrum of 1 were absent in that of 2, and in their place two doublets(]= 14Hz)at66.22and7.65 appeared. The aromatic regions of both spectra were identical. These data indicated that 2 is identical with alatamide, which was previously isolated (11)from the South Indian tree Pleiospmiurn alaturn (Wight and Am.) Swingle (Rutaceae). Full 'H-nmr data were, however, not published. A third crystalline compound isolated was readily shown to be stigmasterol by comparison of mp, ir, and 'H-nmr spectra with those of an authentic sample. Compound 1 has been known for a long time (2,4), but this is the first report of its occurrence as a natural product and of its full spectral data. It is interesting that both tembamide acetate E11 and alatamide 121 were isolated from the plant P. guayranum, while there was no evidence of tembamide 131, their putative biogenetic precursor. Further, it is noteworthy that P-phenylethylamine-derived amides, which are of taxonomic significance in the Rutaceae family, have now been isolated from a member of the Piperaceae. EXPERIMENTAL GENEW EXPERIMENTAL PROCEDURE3.Melting points were determined on a Reichert micro melting point apparatus and are uncorrected. Uv spectra were recorded on a PerkinElmer 552A uv-vis spectrophotometer, and ir spectra were run as Nujol mulls using a Pye Unicam SP3-200 instrument. 'H-(80 MHz) and '3C-(20 M H t ) nmr spectra were run on a Bruker W P 80 SY FT nmr spectrometer with This as internal standard. Lreims were obtained at 70 eV on a KratdAEI MS902 or a Finnegan 4000 mass
Amides from Piper
4 13
spectrometer while hreims were obtained with a KratdAEI MS5O instrument. Si gel 60 PF-254 and 366 (Merck) was used for analytical (0.25 rnm) and preparative (1mm) tlc and for vlc (12). PLANT MATERIAL.-Aerial
parts of the p h t
P. guayrunrm were collected in April 1985 near the 73/4mile post along the Blanchisseuse Road, Arima, Trinidad. A voucher specimen is on deposit at the National Herbarium of Trinidad and Tobago. The plant material was airdried (ca. 304 for 1 week. EXTRACTION.SEPARATION, AND ISOLATION.-The dried, ground plant material (0.7 kg) was exhaustively extracted with Me,CO (10 liters) over 2 days. Evaporation of the Me2C0 gave the crude extract (32.8g). A portion (15g) of the extract was subjected to vlc eluting first with petroleum ether and then with increasing proportions of Me2C0. Fractions 3 2 4 were combined to give a mixture (4g) which was rechromatographed as described above, to yield three crystalline compounds. The major, most polar compound, amide 1, was obtained as white crystalline needles (36mg), mp 159'(petroIeum ether/Me,CO) [lit. (4)140141q;uv(MeOH)Amax208,225,270,278 nm (E 14200, 28200,3100, 2300);ir Y rnax 3315, 1727, 1637, 1532, 1510, 1250, 1232, 1026, 817, 798, 715, 687 cm-'; eims m/z (%) IMl+ 313.1308 (0.7), 253.1121 (12), 192.0805 (14.5), 137.0607 (27), 134.0627 (ll), 117.0582(loo),105.0341(24),105.0702(12), 77.0388 (31);'H nmr see Table 1; I3C nmr see Table 2. Compound 2 was also obtained as white needles (6 mg), rnp 188-189' (petroleum ether/ Me,CO) [lit. (11) 178-1803;uv (MeOH) A rnax 204,222,308nm(E 10700,13400,17200);ir u rnax 3320, 1640,1290,1250,1170, 1030,945 cm-'; eims m/z (%)[MI+ 253 (40),150 (6),149 (6),148 (6),135 (13). 134 (21),121 (11),105 (loo),77 (30);'H nmr see Table 1. The least polar compound, obtained as white crystals (10 mg), was identical in its mp and in its ir and 'Hnmr spectra with stigmasterol.
MILD ALKALINE HYDROLYSIS OF 1 . 4 m pound 1 (12mg)was stirred overnight at room temperature with 10 ml of 10% Na2C03 in MeOWH,O. M e r the usual workup white crystals (10mg) of compound 3 were obtained, mp 147-148' [lit. (7)149-15 17;uv (MeOH) A rnax 209,224,270,279 n m ( ~11400,20500,2190, 1490);ir Y max 3440, 1655, 1595, 1520,1225 cm-'; eims d z (%) [M - H20]+ 253 (6),150 (37),138 (ll),137 (32),136 (38),135 (loo), 134 (58),117 (48),109 (1l), 105 (7l),94 (1l), 78 (lo),77 (60);'H nmr see Table 1. ACKNOWLEDGMENTS The authors wish to thank the staff at the Na-
4 14
tional Herbarium of our University and especially
Mr.M.B.Kalloo for assistance in the collection a d identification of the plant material. We are grateful to Prof. Edward Piers of the University of British Columbia, Vancouver, Canada and Dr. Keith Pascoe of the U.W.I., Mona,Jamaica, for kindly obtaining mass spectra of our compounds. We are also indebted to the U.W.I. for financial support. LITERATURE CITED D. Philcox, "Flora of Trinidad and Tobago," Ministry of Agriculture, Lands and Fisheries, Trinidad and Tobago, 1977, Vol. 11, Part VIII, pp. 527-529. 2. C. Mannich and E. Thiele, A d . Phann. (Weinhint, Ger.), 253, 181 (1915). 3. R. Somanathan, H . Aguilar, G.R. Vennua, and K.M. Smith, Synth. Conmrm., 13,273 (1980). 4. S.M. Albonico, A.M. Kuck, and V. 1.
Wo1. 5 2 , No. 2
Journal of Natural Products 5.
6.
7. 8. 9. 10. 11. 12.
Deulofeu,]. C h .Sw., 1327 (1967). S.R. Johns, J.A. Lamberton, and J.R. Price, A u t . ]. C h . , 20,2795 (1967). S.R. Johns, J.A. Lambeiton, H.J. Tweeddale, and R.I. Willing, A u t . ] . C h . ,22, 2233 (1969). D. Della Casa de Marcano, M.Hasegawa, and A. Castaldi, Phytwhistty, 11, 1531 (1972). E.R. Krajniak, E. Ritchie, and W.C. Taylor, A u t . ] . C h . ,26,687 (1973). A. Shoeb, R.S. Kapil, and S.P. Popli, P h y t w h h y , 12,2071 (1973). H.O. Bemhard and K. Thiel, Helv. Chin. A&, 61,2269 (1978). A. Chatergee, M.Chacrabarry, and A.B. Kundu, A u t . ]. C h . ,28,457(1925). S.W. Pelletier, H.P. Chokshi, and H.K. Desai,]. Nat. Prod., 49, 892 (1986).
R a e i d 8 Sept&
1988
